The invention relates to a sealing device for a fluid-tight screw connection to a hydraulic or pneumatic component.
A known sealing device of this kind has a so-called U-seal sealing ring. This is a metal ring into whose hole the actual sealing ring comprised of rubber elastic material is vulcanized. The sealing ring has a trapezoidal ring cross section, wherein the shorter of the parallel trapezoid edges is vulcanized onto the metal ring and the circumferential edges of the sealing ring at the corners of the longer bottom end of the trapezoid cross section constitute protruding sealing lips. The U-seal sealing ring is placed, for example, under the head of a screwed sealing plug or a radial flange of a screw bushing, which is screwed into a fluid-carrying threaded hole of a component. The screw head or the bushing flange mechanically transmits energy onto the component via the metal ring of the U-seal sealing ring. At the same time, the metal ring predetermines the deformation of the actual sealing ring. The actual sealing ring rests against the underside of the screw head or the tubular bushing and against a surface of the component and seals the screw or screw bushing against the component. This type of seal has the disadvantage that the production of the U-seal sealing ring with the metal ring and the vulcanized-on rubber elastic sealing ring is relatively complex and therefore expensive.
Furthermore, it is known to provide the mouth of the internally threaded bore in the component with a countersink into which a rubber elastic sealing ring is inserted that protrudes beyond the surface of the component, for example an O-ring or a rectangular sealing ring. When the screw or bushing is screwed in, the sealing ring is elastically compressed onto a bottom of the countersink and therefore rests sealingly against the bottom of the countersink and against the underside of the screw head or the bushing flange. The energy is transmitted from the underside of the screw head or the bushing flange directly onto the surface of the component. This sealing device, though, has the disadvantage that when the screw or screw bushing is screwed in, the sealing ring is stressed in the tangential direction, by means of which in particular, a rectangular sealing ring can reach into a gap between the underside of the screw head or bushing flange and the component and can get caught there, which damages the sealing ring. Furthermore, the jammed sealing ring causes an extrusion gap into which the pressurized sealing material flows, which quickly leads to the failure of the sealing device. Moreover, the friction when the screw or screw bushing is tightened, and thereby the starting torque, changes as a result of the sealing material caught between the underside of the screw head or the bushing flange and the component, which can likewise lead to the failure of the sealing device. An O-ring can become twisted as a result of the tangential force when screwing in the screw or the screw bushing, which likewise impairs its sealing function and can lead to the destruction of the O-ring.